See-through display device

ABSTRACT

A see-through display device includes an image generation unit configured to emit a virtual image light, a light combining unit configured to combine the virtual image light with an actual image light, and a driving unit including a deformation unit and a bridge unit disposed between the deformation unit and the image generation unit, and configured to control a distance between the image generation unit and the light combining unit through the deformation unit and the bridge unit.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Korean Patent Application No.10-2018-0126314, filed on Oct. 22, 2018 in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference in its entirety.

BACKGROUND 1. Field

Apparatuses and methods consistent with exemplary embodiments relate tosee-through display devices.

2. Description of the Related Art

Recently, as the development of electronic and display devices that mayrealize virtual reality (VR), interests with respect to VR haveincreased. As a next step of VR, technologies (methods) that may realizeaugmented reality (AR) and mixed reality (MR) have been studied.

Unlike VR that premises a complete virtual world, AR is a displaytechnique that further increases an effect of reality by overlapping(combining) imaginal objects or information on an environment of thereal world. Considering that VR is limitedly applicable to a field, suchas games or virtual experiences, AR may be applicable to various realenvironments. In particular, AR draws attention as a next generationdisplay technique suitable for a ubiquitous environment or an internetof things (IoT) environment. AR may be an example of MR in that AR mixesthe real world and additional information (virtual world).

SUMMARY

One or more exemplary embodiments provide miniaturized and lightweightsee-through display devices.

One or more exemplary embodiments provide see-through display devicesconfigured to continuously change a focal distance thereof.

According to an aspect of an example embodiment, there is provided asee-through display device including: an image generation unitconfigured to emit virtual image light; a light combining unitconfigured to combine the virtual image light and actual image light;and a driving unit including a deformation unit and a bridge unitdisposed between the deformation unit and the image generation unit, andconfigured to control a distance between the image generation unit andthe light combining unit through the deformation unit and the bridgeunit.

A length of the deformation unit may change according to a temperatureof the deformation unit.

The driving unit may further include a driving control unit thatcontrols the deformation unit, and the driving control unit may controlthe temperature of the deformation unit by applying an electricalsignal.

As the length of the deformation unit decreases, the bridge unit maymove the image generation unit closer to the light combining unit todecrease the distance between the image generation unit and the lightcombining unit.

The deformation unit may include a shape memory alloy (SMA).

The deformation unit may be wound around both edges of the bridge unitso that the bridge unit has an arch shape.

The bridge unit may have elasticity.

The both edges of the bridge unit may include recess regions, and thedeformation unit may be wound around the recess regions.

According to an aspect of another example embodiment, there is provideda see-through display device including: an image generation unitconfigured to emit a virtual image light; a light combining unitconfigured to combine the virtual image light and an actual image light;and a driving unit including: a supporting unit; and a deformation unitdisposed between the supporting unit and the image generation unit andconfigured to move the image generation unit closer to the lightcombining unit as a length of the deformation unit increases, whereinthe driving unit may be configured to control a distance between theimage generation unit and the light combining unit through thedeformation unit and the supporting unit.

The driving unit may further include a driving control unit configuredto control the deformation unit, and the driving control unit maycontrol the length of the deformation unit by applying an electricalsignal to the deformation unit.

The length of the deformation unit may be changed according to atemperature of the deformation unit, and the temperature of thedeformation unit may be controlled by the electrical signal.

The see-through display device may further include a restoration unitprovided between the supporting unit and the image generation unit, andthe restoration unit may have a characteristic of returning to aninitial state when the restoration unit is deformed.

The restoration unit may include a bar having elasticity, and both edgesof the bar respectively may contact the supporting unit and the imagegeneration unit.

The bar may be provided a pair of torsion springs, and the pair of barsmay extend in a direction crossing each other.

The restoration unit may include a torsion spring, and both edges of thetorsion spring respectively may contact the supporting unit and theimage generation unit.

The torsion spring may be provided a pair, and the pair of torsionsprings may face each other with the supporting unit and the imagegeneration unit therebetween.

According to an aspect of another example embodiment, there is provideda see-through display device including: an image generation unitconfigured to emit virtual image light; a light combining unitconfigured to form a virtual image based on the virtual image light; adeformation unit configured to control a distance between the virtualimage and the light combining unit; and a driving control unitconfigured to control a length of the deformation unit to adjust thedistance between the virtual image and the light combining unit.

The driving control unit may increase the distance between the virtualimage and the light combining unit by reducing the length of thedeformation unit.

The see-through display device may further include a bridge unitdisposed between the deformation unit and the image generation unit,wherein as the length of the deformation unit decreases, the bridge unitmoves the image generation unit closer to the light combining unit, andas the image generation unit is disposed closer to the light combiningunit, the distance between the virtual image and the light combiningunit 300 is increased.

The driving control unit may increase the distance between the virtualimage and the light combining unit by increasing the length of thedeformation unit.

The see-through display device may further include: a supporting unitspaced apart from the image generation unit with the deformation unitthat is disposed between the supporting unit and the image generationunit; and a restoration unit arranged between the supporting unit andthe image generation unit, wherein as the length of the deformation unitincreases, the image generation unit is disposed closer to the lightcombining unit, and as the image generation unit is disposed closer tothe light combining unit, the distance between the virtual image and thelight combining unit is increased.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects will be more apparent by describingcertain example embodiments, with reference to the accompanying drawingsin which:

FIG. 1 is a block diagram of a see-through display device according toan example embodiment;

FIG. 2 is a conceptual drawing of a see-through display device accordingto an example embodiment;

FIG. 3 is a perspective view of a bridge unit of FIG. 2;

FIG. 4 is a perspective view of a driving unit of FIG. 2;

FIGS. 5 and 6 are conceptual drawings for explaining an operation of thesee-through display device of FIG. 2;

FIGS. 7 and 8 are conceptual drawings for explaining an operation of asee-through display device according to another example embodiment;

FIGS. 9 and 10 are conceptual drawings for explaining an operation of asee-through display device according to another example embodiment; and

FIGS. 11 and 12 are conceptual drawings for explaining an operation of asee-through display device according to another example embodiment.

DETAILED DESCRIPTION

Example embodiments are described in greater detail below with referenceto the accompanying drawings.

In the following description, like drawing reference numerals are usedfor like elements, even in different drawings. The matters defined inthe description, such as detailed construction and elements, areprovided to assist in a comprehensive understanding of the exampleembodiments. However, it is apparent that the example embodiments can bepracticed without those specifically defined matters. Also, well-knownfunctions or constructions are not described in detail since they wouldobscure the description with unnecessary detail.

It will also be understood that when an element is referred to as being“on” or “above” another element, the element may be in direct contactwith the other element or other intervening elements may be present.

In the following embodiments, the singular forms include the pluralforms unless the context clearly indicates otherwise. It should beunderstood that, when a part “comprises” or “includes” an element in thespecification, unless otherwise defined, other elements are not excludedfrom the part and the part may further include other elements.

Also, in the specification, the term “units” or “ . . . modules” denoteunits or modules that process at least one function or operation, andmay be realized by hardware, software, or a combination of hardware andsoftware.

Expressions such as “at least one of,” when preceding a list ofelements, modify the entire list of elements and do not modify theindividual elements of the list. For example, the expression, “at leastone of a, b, and c,” should be understood as including only a, only b,only c, both a and b, both a and c, both b and c, all of a, b, and c, orany variations of the aforementioned examples.

FIG. 1 is a block diagram of a see-through display device 10 accordingto an example embodiment.

Referring to FIG. 1, the see-through display device 10 including animage generation unit 1, a driving unit 2, and a light combining unit 3may be provided. The term “see-through display device” may be alsoreferred to as “transparent display device.” The see-through displaydevice 10 may be a device that combines actual image light with virtualimage light and provides the combined light to a user. The actual imagelight may be light that is emitted from an actual object and includesimage information with respect to the actual object. The virtual imagelight may be light that is emitted from, for example, a display device,such as a spatial light modulator (SLM) and includes required virtualimage information.

The image generation unit 1 may emit virtual image light. For example,the image generation unit 1 may include a liquid crystal on silicon(LCoS). The driving unit 2 may control a location of the imagegeneration unit 1. For example, the driving unit 2 may adjust a locationof the image generation unit 1 so that the image generation unit 1 maybe placed close to the light combining unit 3 or away from the lightcombining unit 3. The light combining unit 3 may combine a virtual imagewith an actual image. For example, the light combining unit 3 mayinclude a beam splitter.

FIG. 2 is a conceptual drawing of a see-through display device 11according to an example embodiment. FIG. 3 is a perspective view of abridge unit 220 of FIG. 2. FIG. 4 is a perspective view of a drivingunit 200 of FIG. 2.

Referring to FIGS. 2 through 4, the see-through display device 11including an image generation unit 100, the driving unit 200, and alight combining unit 300 may be provided.

The image generation unit 100 may emit virtual image light. For example,the image generation unit 100 may include an LCoS and a light source.The image generation unit 100 may provide virtual image light to thelight combining unit 300.

The driving unit 200 may control a location of the image generation unit100. The driving unit 200 may include a first deformation unit 210, abridge unit 220, and a driving control unit 230. The first deformationunit 210 may be of a wire type. A length of the first deformation unit210 may vary according to a temperature of the first deformation unit210 and an electric field formed in the first deformation unit 210. Forexample, the first deformation unit 210 may include a shape memory alloy(SMA), an electro-active polymer (EAP), and a combination of thesematerials. When the first deformation unit 210 includes an SMA, thefirst deformation unit 210 may have a relatively small length at arelatively high temperature and may have a relatively large length at arelatively low temperature. For example, the length of the firstdeformation unit 210 may increase as the temperature of the firstdeformation unit 210 decreases, and the length of the first deformationunit 210 may decrease as the temperature of the first deformation unit210 increases. When the first deformation unit 210 includes an EAP, alength of the first deformation unit 210 may extend in a directionvertical to an electric field when the electric filed is applied to thefirst deformation unit 210. For convenience of explanation, hereinafter,the deformation of the first deformation unit 210 by temperature will bedescribed.

The temperature of the first deformation unit 210 may be controlled byan electrical signal applied to the first deformation unit 210. Theelectrical signal may be applied by the driving control unit 230. Thedriving control unit 230 may include a voltage supply, a current supply,or a power supply to generate the electrical signal. The electricalsignal may be a voltage signal or a current signal. For example, thetemperature of the first deformation unit 210 may change according to avalue of the voltage signal or the current signal that is applied to thefirst deformation unit 210. In an example embodiment, the temperature ofthe first deformation unit 210 may be increased by applying a voltage tothe first deformation unit 210 by the driving control unit 230. When avoltage is not applied to the first deformation unit 210, thetemperature of the first deformation unit 210 may be reduced. As such,the driving unit 200 may apply heat to the first deformation unit 210 byusing an electrical signal, so that the temperature of the firstdeformation unit 210 may change as a result of the supply of heat.

The bridge unit 220 may be arranged between the first deformation unit210 and the image generation unit 100. As depicted in FIGS. 3 and 4, thebridge unit 220 may include a plate type member extending in adirection. The bridge unit 220 may include recess regions 220 a, 220 b,220 c, and 220 d facing each other on both edges in an extendingdirection. The recess regions 220 a, 220 b, 220 c, and 220 d may be usedto fixate the first deformation unit 20 at the edges of the bridge unit220, and may be also referred to as the term “depressions” or “grooves.”

The bridge unit 220 may have elasticity. The bridge unit 220 may be ofan arch type by bending by the first deformation unit 210. Edge units ofthe bridge unit 220 may be wound by the first deformation unit 210. Thefirst deformation unit 210 may be wound around the recess regions 220 a,220 b, 220 c, and 220 d of the edge units of the bridge unit 220. Therecess regions 220 a, 220 b, 220 c, and 220 d may fix the firstdeformation unit 210 to the bridge unit 220. Accordingly, locations ofthe first deformation unit 210 and the bridge unit 220 may be arranged.The degree of bending of the bridge unit 220 may vary according to thelength change of the first deformation unit 210. The term “degree ofbending” may be also referred to as “degree of curve” or “degree ofcurvature.” When the length of the first deformation unit 210 isreduced, the degree of bending of the bridge unit 220 may be increased.Accordingly, a distance between the image generation unit 100 and thelight combining unit 300 may be reduced. When the length of the firstdeformation unit 210 is increased, the degree of bending of the bridgeunit 220 may be reduced. Accordingly, the distance between the imagegeneration unit 100 and the light combining unit 300 may be increased.

The light combining unit 300 may combine a virtual image with an actualimage. The light combining unit 300 may include a light combiningelement 310 and a light focusing element 320. The light focusing element320 may reflect and focus virtual image light incident to the lightfocusing element 320. For example, the light focusing element 320 mayinclude a concave mirror, a convex lens, or a combination of the concavemirror and the convex lens. When the light focusing element 320 includesa convex lens, the light focusing element 320 may be disposed betweenthe light combining element 310 and the image generation unit 100. Forconvenience of explanation, hereinafter, a case that the light focusingelement 320 includes a concave lens will be described.

The image generation unit 100 may be arranged between the light focusingelement 320 and a focal point of the light focusing element 320.Accordingly, a virtual image with respect to an image generated by theimage generation unit 100 may be formed.

The light combining element 310 may reflect a portion of light incidentto the light combining element 310 and may transmit the other portionthereof. For example, the light combining element 310 may include a cubebeam splitter or a plate beam splitter. For convenience of explanation,it is depicted as that the light combining element 310 includes a cubebeam splitter.

Various optical elements may further be disposed between the imagegeneration unit 100 and the light combining unit 300. For example,optical elements for controlling a length of a light path may bedisposed between the image generation unit 100 and the light combiningunit 300.

FIGS. 5 and 6 are conceptual drawings for explaining an operation of asee-through display device 11 of FIG. 2. For convenience of explanation,descriptions substantially identical to the descriptions made withreference to FIGS. 2 through 4 may be omitted.

In FIG. 5, the driving control unit 230 may not apply a voltage or acurrent to the first deformation unit 210, whereas the driving controlunit 230 in FIG. 6 may apply a voltage or current to the firstdeformation unit 210.

With reference to FIG. 5, the image generation unit 100 may be spacedapart from the light combining element 310 as much as a distance Y₁. Theimage generation unit 100 may emit virtual image light. The virtualimage light may transmit through the light combining element 310. Aportion of the virtual image light may be reflected by the lightcombining element 310. The virtual image light that is transmittedthrough the light combining element 310 may reach the light focusingelement 320.

The light focusing element 320 may generate reflected light byreflecting the virtual image light. The reflected light may be virtualimage light reflected by the light focusing element 320. The reflectedlight may be reflected by the light combining element 310 and may befocused on the eyes of a user 500 of the see-through display device 11.Accordingly, the user 500 may observe a virtual image generated by theimage generation unit 100. Although not shown, a portion of thereflected light may transmit through the light combining element 310.

The image generation unit 100 may be arranged between the light focusingelement 320 and a focal point of the light focusing element 320.Accordingly, the light combining unit 300 may form a virtual image 400.The virtual image 400 may be spaced apart from the light combiningelement 310 as much as a distance X₁.

Referring to FIG. 6, a temperature of the first deformation unit 210 maybe increased by applying a voltage to the first deformation unit 210.The voltage may be applied by the driving control unit 230. Accordingly,a length of the first deformation unit 210 may be reduced. The degree oflength change of the first deformation unit 210 may be controlled bycontrolling the temperature of the first deformation unit 210.

The degree of bending of the bridge unit 220 may be increased. Thebridge unit 220 may dispose the image generation unit 100 closer to thelight combining unit 300 by pushing the image generation unit 100 towardthe light combining element 310. The image generation unit 100 and thelight combining element 310 may be spaced apart as much as a distanceY₂, which is less than the distance Y₁.

The virtual image 400 may move away from the light combining unit 300.The virtual image 400 may be spaced apart from the light combiningelement 310 as much as a distance X₂, which is greater than the distanceX₁. In other words, the virtual image 400 in FIG. 6 may be projected ata position further far away from the light combining element 310,compared to the virtual image 400 in FIG. 5.

Once the driving control unit 230 stops applying a voltage to the firstdeformation unit 210, the temperature of the first deformation unit 210may be reduced. The length of the first deformation unit 210 may bere-increased to the length as shown in FIG. 5. The degree of bending ofthe bridge unit 220 may be reduced. The image generation unit 100 may bemoved away from the light combining unit 300. For example, the imagegeneration unit 100 may move towards the light combining element 310 bya distance Y₁ from the light combining element 310. The virtual image400 may be closer to the light combining unit 300. For example, thevirtual image 400 and the light combining element 310 may be closer toeach other by the distance X₁.

The present disclosure may provide the see-through display device 11configured to control a location of the virtual image 400. The locationof the virtual image 400 may be continuously changed.

The present disclosure may provide the see-through display device 11 inwhich the driving unit 200 that moves the location of the imagegeneration unit 100 is miniaturized and lightweight

FIGS. 7 and 8 are conceptual drawings for explaining operations of asee-through display device 12 according to another example embodiment.For convenience of explanation, descriptions substantially identical tothe descriptions made with reference to FIG. 2 will be omitted.

Referring to FIG. 7, the see-through display device 12 including animage generation unit 100, a driving unit 200, and a light combiningunit 300 may be provided. The image generation unit 100 and the lightcombining unit 300 may be substantially identical to the imagegeneration unit 100 and the light combining unit 300 described withreference to FIG. 2.

The driving unit 200 may control of a location of the image generationunit 100. The driving unit 200 may include second deformation units 212,a supporting unit 240, and a driving control unit 230. Each of thesecond deformation units 212 may be substantially the same as the firstdeformation unit 210 described with reference to FIG. 2 except forlocations and a shape of the second deformation units 212.

The second deformation units 212 may be arranged between the supportingunit 240 and the image generation unit 100. Edge units of each of thesecond deformation units 212 may contact the supporting unit 240 and theimage generation unit 100, respectively. A pair of the seconddeformation units 212 are depicted in FIG. 7, but it is an example. Insome other embodiments, a single deformation unit 212 or more than threesecond deformation units 212 may be provided.

The driving control unit 230 is electrically connected to the seconddeformation units 212 and may apply an electrical signal to the seconddeformation units 212. For example, the driving control unit 230 mayapply a voltage or a current to the second deformation units 212.

The driving control unit 230 of FIG. 7 may not apply an electricalsignal to the second deformation units 212. The image generation unit100 may be spaced apart from the light combining element 310 as much asa distance Y₁. The image generation unit 100 may emit virtual imagelight. As described with reference to FIGS. 5 and 6, the light combiningunit 300 may form a virtual image 400. The virtual image 400 may bespaced apart from the light combining element 310 as much as a distanceX₁.

Referring to FIG. 8, a temperature of the second deformation units 212may be increased by applying an electrical signal to the seconddeformation units 212. For example, the electrical signal may be avoltage signal or a current signal. The voltage signal may be applied bythe driving control unit 230. A length of each of the second deformationunits 212 may be reduced. The image generation unit 100 may move awayfrom the light combining element 310. The image generation unit 100 andthe light combining element 310 may be spaced apart as much as adistance Y₂, which is greater than the distance Y₁. The degree of lengthchange of each of the second deformation units 212 may be controlled bycontrolling the temperature of the second deformation units 212.

The virtual image 400 may move closer to the light combining unit 300.The virtual image 400 and the light combining element 310 may be spacedapart from each other as much as a distance X₂, which is less than thedistance X₁.

Once the driving control unit 230 stops applying a voltage or currentsignal to the second deformation units 212, the temperature of thesecond deformation units 212 may be reduced, and the shape of seconddeformation units 212 and the location of the image generation unit 100in FIG. 8 may return to the shape and the location as shown in FIG. 7.Specifically, a length of the second deformation units 212 may bere-increased. The image generation unit 100 may move closer to the lightcombining unit 300. For example, the image generation unit 100 may movefrom the light combining element 310 as much as the distance Y₁. Thevirtual image 400 may move away from the light combining unit 300. Forexample, the virtual image 400 and the light combining element 310 maybe spaced apart from each other by the distance X₁.

The present disclosure may provide the see-through display device 12configured to control a location of the virtual image 400. The locationof the virtual image 400 may be continuously changed.

The present disclosure may provide the see-through display device 12 inwhich the driving unit 200 that moves the location of the imagegeneration unit 100 is miniaturized and lightweight.

FIGS. 9 and 10 are conceptual drawings for explaining an operation of asee-through display device 13 according to another example embodiment.For convenience of explanation, descriptions substantially identical tothe descriptions made with reference to FIGS. 7 and 8 will be omitted.

Referring to FIG. 9, the see-through display device 13 including animage generation unit 100, a driving unit 200, and a light combiningunit 300 may be provided. The image generation unit 100 and the lightcombining unit 300 may be substantially the same as the image generationunit 100 and the light combining unit 300 described with reference toFIGS. 7 and 8.

The driving unit 200 may control a location of the image generation unit100. The driving unit 200 may include second deformation units 212, asupporting unit 240, and first restoration units 252, and a drivingcontrol unit 230. The second deformation units 212, the supporting unit240, and the driving control unit 230 may be substantially the same asthe second deformation units 212, the supporting unit 240, and thedriving control unit 230 described with reference to FIGS. 7 and 8.

The first restoration units 252 may be provided between the supportingunit 240 and the image generation unit 100. The first restoration units252 may extend towards the image generation unit 100 from the supportingunit 240. The first restoration units 252 may extend to cross eachother. Edge units of each of the first restoration units 252respectively may contact the supporting unit 240 and the imagegeneration unit 100. The first restoration units 252 may haveelasticity. For example, each of the first restoration units 252 mayinclude a bar including carbon. When the first restoration units 252 arebent, the first restoration units 252 may have restoration force to berestored to a state before bending.

The driving control unit 230 of FIG. 9 may not apply an electricalsignal to the second deformation units 212. The image generation unit100 may be spaced apart from the light combining element 310 as much asthe distance Y₁. A virtual image 400 may be spaced apart from the lightcombining element 310 as much as the distance X₁.

Referring to FIG. 10, a temperature of the second deformation units 212may be increased by applying an electrical signal to the seconddeformation units 212. For example, the electrical signal may be avoltage signal. The voltage signal may be applied by the driving controlunit 230. A length of each of the second deformation units 212 may bereduced. The image generation unit 100 may move away from the lightcombining element 310. The image generation unit 100 and the lightcombining element 310 may be spaced apart from each other as much as adistance Y₂, which is greater than the distance Y₁. The degree of lengthchange of each of the second deformation units 212 may be controlled bycontrolling the temperature of the second deformation units 212.

The virtual image 400 may be closer to the light combining unit 300. Thevirtual image 400 and the light combining element 310 may be spacedapart from each other as much as a distance X₂, which is less than thedistance X₁.

The first restoration units 252 may be bent by the image generation unit100 and the supporting unit 240. Accordingly, the first restorationunits 252 may have a restoration force. The restoration force may act ina direction of increasing a distance between the image generation unit100 and the supporting unit 240.

Once the driving control unit 230 stops applying a voltage or currentsignal to the second deformation units 212, the temperature of thesecond deformation units 212 is reduced and the length of the seconddeformation units 212 may be re-increased to return back to the state asshown in FIG. 9. Accordingly, the image generation unit 100 may belocated closer to the light combining unit 300. For example, the imagegeneration unit 100 may move towards the light combining element 310 bya distance Y₁ from the light combining element 310. The virtual image400 may move away from the light combining unit 300. For example, thedistance from the virtual image 400 to the light combining element 310may be increased to the distance X₁.

The present disclosure may provide the see-through display device 13configured to control a location of the virtual image 400. The locationof the virtual image 400 may be continuously changed.

The present disclosure may provide the see-through display device 13 inwhich the driving unit 200 that moves the location of the imagegeneration unit 100 is miniaturized and lightweight.

FIGS. 11 and 12 are conceptual drawings for explaining an operation of asee-through display device 14 according to example embodiments. Forconvenience of explanation, descriptions substantially identical to thedescriptions made with reference to FIGS. 7 and 8 will be omitted.

Referring to FIG. 11, the see-through display device 14 including animage generation unit 100, a driving unit 200, and a light combiningunit 300 may be provided. The image generation unit 100 and the lightcombining unit 300 are substantially the same as the image generationunit 100 and the light combining unit 300 described with reference toFIGS. 7 and 8.

The driving unit 200 may control a location of the image generation unit100. The driving unit 200 may include second deformation units 212, asupporting unit 240, second restoration units 254, and a driving controlunit 230. The second deformation units 212, the supporting unit 240, andthe driving control unit 230 are substantially the same as the seconddeformation units 212, the supporting unit 240, and the driving controlunit 230 described with reference to FIGS. 7 and 8.

The second restoration units 254 may be arranged between the supportingunit 240 and the image generation unit 100. The second restoration units254 may include torsion springs. When the second restoration units 254are distorted, the second restoration units 254 may have restorationforce to be restored to a state before distortion. Edge units of each ofthe second restoration units 254 may contact the supporting unit 240 andthe image generation unit 100, respectively.

The driving control unit 230 of FIG. 11 may not apply an electricalsignal to the second deformation units 212. The image generation unit100 may be spaced apart from the light combining element 310 as much asthe distance Y₁. The virtual image 400 may be spaced apart from eachother as much as the distance X₁.

Referring to FIG. 12, a temperature of the second deformation units 212may be increased by applying an electrical signal to the seconddeformation units 212. For example, the electrical signal may be avoltage signal. The voltage signal may be applied by the driving controlunit 230. A length of each of the second deformation units 212 may bereduced. The image generation unit 100 may move away from the lightcombining element 310. The image generation unit 100 and the lightcombining element 310 may be spaced apart as much as a distance Y₂ whichis greater than the distance Y₁. The degree of length change of each ofthe second deformation units 212 may be controlled by controlling thetemperature of the second deformation units 212.

The virtual image 400 may move closer to the light combining unit 300.The virtual image 400 and the light combining element 310 may be spacedapart from each other as much as a distance X₂, which is less than thedistance X₁.

When the image generation unit 100 and the supporting unit 240 arecloser to each other, the second restoration units 254 may be twisted.Accordingly, the second restoration units 254 may have a restorationforce to be returned to an initial state. The restoration force may actin a direction of increasing the distance between the image generationunit 100 and the supporting unit 240.

Once the driving control unit 230 stops applying a voltage/current tothe second deformation units 212, the temperature of the seconddeformation units 212 is reduced and the length of the seconddeformation units 212 may be increased to return back to the state asshown in FIG. 11. The image generation unit 100 and the light combiningunit 300 may be closer to each other. For example, the image generationunit 100 may move towards the light combining element 310 by a distanceY₁ from the light combining element 310. The virtual image 400 may bespaced apart from the light combining unit 300. For example, the virtualimage 400 may be spaced apart from the light combining element 310 by adistance X₁.

The present disclosure may provide the see-through display device 14configured to control a location of the virtual image 400. The locationof the virtual image 400 may be continuously changed.

The present disclosure may provide the see-through display device 14 inwhich the driving unit 200 that moves the location of the imagegeneration unit 100 is miniaturized and lightweight.

The present disclosure provides a miniaturized and lightweightsee-through display device.

The present disclosure provides a see-through display device configuredto continuously change a focal distance.

The foregoing exemplary embodiments are merely exemplary and are not tobe construed as limiting. The present teaching can be readily applied toother types of apparatuses. Also, the description of the exemplaryembodiments is intended to be illustrative, and not to limit the scopeof the claims, and many alternatives, modifications, and variations willbe apparent to those skilled in the art.

What is claimed is:
 1. A see-through display device comprising: an imagegeneration unit that comprises a light source and is configured to emita virtual image light; a light combining unit that comprises a mirrorand a beam splitter and is configured to combine the virtual image lightwith an actual image light; and a driver comprising a deformation unithaving a length that changes according to heat applied to thedeformation unit, and a bridge disposed between the deformation unit andthe image generation unit, and configured to control a distance betweenthe image generation unit and the light combining unit through thedeformation unit and the bridge.
 2. The see-through display device ofclaim 1, wherein the length of the deformation unit is changed accordingto a temperature of the deformation unit.
 3. The see-through displaydevice of claim 2, wherein the driver further comprises a drivingcontroller that controls the deformation unit, and the drivingcontroller controls the temperature of the deformation unit by applyingan electrical signal to the deformation unit.
 4. The see-through displaydevice of claim 2, wherein, as the length of the deformation unitdecreases, the bridge moves the image generation unit closer to thelight combining unit to decrease the distance between the imagegeneration unit and the light combining unit.
 5. The see-through displaydevice of claim 2, wherein the deformation unit comprises a shape memoryalloy (SMA).
 6. The see-through display device of claim 1, wherein thedeformation unit is wound around two opposing edges of the bridge sothat the bridge has an arch shape.
 7. The see-through display device ofclaim 6, wherein the two opposing edges of the bridge comprise recessregions, and the deformation unit is wound around the recess regions. 8.The see-through display device of claim 1, wherein the driver is furtherconfigured to apply heat to the deformation unit to change a degree ofcurvature of the bridge, and change the distance between the imagegeneration unit and the light combining unit in accordance with thechanged degree of curvature of the bridge.
 9. A see-through displaydevice comprising: an image generation unit that comprises a lightsource and is configured to emit a virtual image light; a lightcombining unit that comprises a mirror and a beam splitter and isconfigured to form a virtual image based on the virtual image light; adeformation unit that has a length changing according to heat applied tothe deformation unit, and is configured to control a distance betweenthe virtual image and the light combining unit; and a driving controllerconfigured to control the length of the deformation unit to adjust thedistance between the virtual image and the light combining unit.
 10. Thesee-through display device of claim 9, wherein the driving controller isfurther configured to increase the distance between the virtual imageand the light combining unit by reducing the length of the deformationunit.
 11. The see-through display device of claim 10, further comprisinga bridge disposed between the deformation unit and the image generationunit, wherein, as the length of the deformation unit decreases, thebridge moves the image generation unit closer to the light combiningunit, and as the image generation unit is disposed closer to the lightcombining unit, the distance between the virtual image and the lightcombining unit is increased.
 12. The see-through display device of claim9, wherein the driving controller is further configured to increase thedistance between the virtual image and the light combining unit byincreasing the length of the deformation unit.
 13. The see-throughdisplay device of claim 12, further comprising: a supporting unit spacedapart from the image generation unit with the deformation unit that isdisposed between the supporting unit and the image generation unit; anda restoration unit arranged between the supporting unit and the imagegeneration unit, wherein as the length of the deformation unitincreases, the image generation unit is disposed closer to the lightcombining unit, and as the image generation unit is disposed closer tothe light combining unit, the distance between the virtual image and thelight combining unit is increased.